Microsoft produces C# and Typescript. Google produced Go and Dart. I think it's fair to say that C# is a better language than Go. The biggest flaw in Go (lack of generics) is met with the weak excuse that they haven't figured out how to do it right. I don't know much about Dart, but Typescript is a stellar language.
Microsoft has a lot of PL expertise in house, including Simon Peyton Jones. Their languages clearly benefit from expertise in PL theory. Google, on the other hand, favors pragmatism over theory and prefers to draw on software engineering experience. Google's languages aren't bad, they just don't seem to have much going for them as languages. Their failings are partly made up for in other things, like the toolchain, libraries, etc.
So I think looking at these real world examples, it's clear that PL theory does lead to better languages, even when one excludes languages like Haskell with little industry adoption.